Main bearings

[ToddK]

I'm trying to find a set of performance main bearings, like the FM 125M, for a crank that is 0.030" undersized. The only 30 under bearings I can find are the full groove style with the feed hole in both the top and bottom shells. Are there any decent performance main bearings available for a 30 under crank?

[Nightmist66]

There are some by King. Full groove with a round hole, no slot. Only one oil hole too. I just installed some .010's on one of mine. They look decent for the money. FWIW:

https://www.summitracing.com/parts/kgb-mb559am030

[chris401]

Were those half groove bearings out of production for a while? Around 2000 I was not online but was on the phone looking.

[ToddK]

I have a set of the King MB559AM030 bearings, they are full groove with 2 oil holes. I think the problem is that the crank is 0.030" undersized, there seems to be a wider range of bearings available for STD, 0.010" and 0.020".

I will just go ahead and use the bearings I have, I'm not expecting this short motor to see much over 6500rpm.

[Nightmist66]

Well, I lied. I took a look at a spare set of King .010 bearings I have, and they do have two oil holes. My bad.